Pneumatically operated floating dry dock



A ril 25, 1967 H. ROBERTS PNEUMATICALLY OPERATED FLOATING DRY DOCK FiledOct. 24, 1965 wmi mv umw 9mm bmm 8N eavm INVENTOR. I HA ROL D ROBERTSme! m! ounuumd A TTORNE Y8 m m km mm United States Patent 3,315,627PNEUMATICALLY OPERATED FLOATING DRY DOCK Harold Roberts, 3600 21st St.,San Francisco, Calif. 94114 Filed Oct. 24, 1965, Ser. No. 504,538 8Claims. (Cl. 11445) This invention relates to a floating dry dock and,more particularly, to a dry dock which may be submerged below thesurface of the water by taking in water as ballast and then beingrefloated to the surface under a vessel which is to be serviced by meansof displacing the 'water ballast with compressed air.

I am familiar with a variety of prior art floating dry docks whichutilize water as ballast to submerge temporarily and then discharge thewater ballast to ascend back to the surface. Such facilities generallyare provided with airtight ballast containers of substantially rigidconstruction, and ballast control is usually achieved by directingcompressed air at certain rates and pressures into the watercompartments to expel the water ballast. The rigid ballast compartmentsimpose a substantial displacing volume which must be overcome by acertain fixed amount of ballast before the dock may be submerged and areof a relatively costly construction. When the dock is resurfaced, atleast a portion of such additional ballast normally must be expelled bythe use of compressed air, thus adding load to the compressed airsystem. Since it is usually desirable to surface a dry dock as rapidlyas is practicable, the compressor should have a capacity sufficient toevacuate the water ballast from all tanks within a relatively short timeperiod. The initial pressure against which the compressor must work,therefore, dictates its maximum pressure capacity at whatever rate ofcubic foot displacement is necessary for a particular application. Thesize of compressor required, i.e. its power rating, is generally afunction of the aforementioned maximum pressure capacity and the timeperiod that such pressure must be delivered. Hence, the longer the timethat a submerged dock remains on the bottom during ballast discharge,the larger must be its compressor.

It is an object of this invention to provide a submergible floatingclock which may be submerged and refloated relatively rapidly using a ofballast and requiring a relatively limited amount of compressed air atmoderate pressures.

More specifically, it is an object to provide a floating dock having atleast one rigid ballast compartment and a pneumatically inflatable bagsecured to the underside of the dock plat-form. When the dock is to besubmerged, the inflatable bag is depressed to its flat deflatedcondition, and the rigid ballast compartment is opened to take in water.The volumetric relationship of the entire dock structure to be submergedand'the volume of the ballast compartment is selected so the docksubmerges when the compartment is filled with water. The dock isrefloated by first blowing the water from the ballast compartment bymeans of compressed air and then conveying air to the pneumaticallyinflatable bag from the ballast compartrnent by interconnecting pipesand valviug. The rigid compartment and inflatable bag may be selected toprovide positive buoyancy to the entire dock structure afterequalization of pressure between the bag and ballast compartment, i.e.the volume of dock structure, ballast compartment and inflated bag is atleast as great as the volume of water equal in weight to the entire dockstructure.

A feature and an advantage of my invention is that once positivebuoyancy is achieved by the equalization of pressure between the ballastcompartment and the inflatable bag, the entire dock structure begins toascend and 3,315,627 Patented Apr. 25, 1967 the flexible inflatable bagwill continue to expand due to the decrease in surrounding hydrostaticpressure. Such continued expansion of the bag will accelerate the speedof ascent of the dock and continue to impart to it increased positivebuoyancy, which is not possible using the wholly rigid tank designs ofthe prior art devices known to me. By proper selection of rigid ballastcompartment and inflatable bag, the positive buoyancy of the dockstructure once at the surface may be sufiicient to support the vessel tobe serviced with associated equipment and personnel, even withoutadditional compressed air delivery to the inflatable bag.

Another feature and advantage of my invention is that the inflatable'bag may be positioned above the rigid ballast tank which also acts as areceiver for air to be transferred to the bag when the dock is to besurfaced. With the bag positioned above ballast tank, the hydro staticpressure.at the elevation of the bag is always less than at the tank andthe pressure of compressed air that may be received by the tank toevacuate water from it. Because of the relatively higher pressure of airin the ballast tank, positive buoyancy may be provided to the dockstructure by transfer of air from the rigid ballast tank to theinflatable bag without the necessity of charging the rigid tank, nowused as a receiver, to an even higher air pressure. Once positivebuoyancy is imparted to the system, the higher elevation of the bag overthe rigid tank accentuates the acceleration of the system to thesurface.

Another object of this invention is to provide a floating dry clock ofthe type described above and wherein the rigid ballast compartment iscomprised of a series of rigid pipe segments in fluid communication withone another.

Another feature and an advantage of this invention is that a majorportion of the compartments necessary to receive air and providepositive buoyancy for reflotation is provided in the form of acollapsible structure, i.e. the inflatable bag or bags. In this way thevolume of dock structure that is displaced during submergence is made assmall as possible, and the amount of ballast which must be taken in tosubmerge the dock, and expelled to refioat it, is minimized.

A further feature and advantage is that the inflatable bag or bags maybe fabricated of rubber, polyethylene, or other suitable collapsible,relatively watertight material which may be easily handled and arerelatively inexpensive.

Another feature and advantage of this invention is that a vessel may bepositioned over the submerged dock While an air compressor expels atleast a portion of the water from the rigid pipe segments. When completereflotation is desired, any remaining water may be expolled from therigid pipe segments in a relatively short ime.

Another feature and advantage of this invention is that the rigid pipesegments may be used as receiver tanks for the inflatable bag which hasbeen in its deflated condition during submergence of the dock.Additional positive buoyancy may be imparted to the dock by transferringair from such receiver tanks to the inflatable bag wtihout further workon the part of the air compressor, and the dock caused to continue torise with mcreasing buoyancy during the rise due to expansion of thebag. This may be achieved by further inflating the rubber bag which isthen at a water depth which requires less pressure for furtherinflation, and during ascent the air already present in the pipesegments and inflatable bag may continue to expand. The partialinflation of the inflatable bag, or bags, by the rigid pipe segmentsacting as a compressed air receiver for the bag distributes thecompressor workload over a longer time period and at a lower averagepressure than would normally be possible if the entire ballast systemwere of rigid pipe construction. Thus a relatively smaller compressormay be used in my invention to refloat a given dock and vessel loadwithin a predetermined total time interval than would normally be thecase using all rigid construction ballast tanks.

Another object of this invention is to provide a floating dry dock ofthe type described above having rigid pipe segments in addition to thosenecessary for the water ballast. Such additional pipe segments may he ofthe ballast type and provide an added degree of stability to the unitduring all stages of operation. If such segments are of the ballasttype, i.e. provided with means for taking in and discharging waterballast, they'may be used to maintain the dock in trim to prevent unduepitching or listing particularly during submergence and re dock in itselevated position during extended periods of vessel repair ormaintenance without having to rely upon maintaining air in the rigidpipe segments or inflatable bag. Moreover, the-compressed air source andpiping may'then be disconnected and used on other docks.

Numerous other objects, features and advantages will become apparent toone of ordinary skill in the art upon a reading of the specificationwhich follows and by making reference to the accompanying drawing.

Turning now to the drawing, 1 show an isometric view of the dry dockembodying my invention with the top planking and structure, shown partlyfragmented to reveal certain details thereunder; the associatedconventional compressor assembly and piping generally are shownschematically.

My invention is best understood by referring to the drawing which showsa dock at A in its floating condition with a vessel indicated at Bsupported thereon by several braces such as the one shown at C. Theplatform portion of the dock indicated at D may be fabricated from a va-7 riety of suitable materials using known construction techniques, andin the example shown a series of wooden planks 11 are joined togetherand supported between the bosoms of I beams 12. Enclosed, hollow,longitudinal pipes 13a are secured under longitudinal edge 14:: of theplatform on one side thereof and a similar series of pipes 131; aresecured under opposite edge 14b. Although various lengths of docks maybe accommodated by my invention, in the particular example shown threestandard lengths of pipe are indicated joined by couplings 16b betweenpipes 13b, and similar couplings (not shown) may be used to join pipes13a. The pipes themduced at any one of a number of mills and maycomprise welded or seamless steel, aluminum, or other similar maselvesmay be of a suitable standard stock product as proterial capable ofresisting the hydrostatic pressures imposed during operation. The pipematerial should be selected to be either non-corrosive or provided witha corrosion-resistant protective layer. Couplings 16b may be of a simplesleeve type, and I have found it desirable to use ordinary rubbercouplings which also give an added degree of flexibility in thelongitudinal direction of the dock. Nonetheless, it may be desirable toreinforce the connected pipe sections and add longitudinal stiffness tothe dock structure by providing elongate reinforcing ribs 20a and 20bunder pipes 13a and 13b, respectively. Such members may be fabricatedfrom wood or the'like, and, together with curved straps 17a and l7baround portions of pipes 13 secured by means of conventional fastenersto the underside of crossbeams 12, secure the pipes to the underside ofthe dock platform structure. underneath the pipes to members 20a and20b, respectively, may be accomplished by means of long, continuous,lateral crossrods 18 which give additional lateral stiifness to the dockstructure.

Ballast tanks 19a and,19b, which may be of construction similar to pipesand 1317 respectively described above, are secured by means of straps21a and 21b, respectively, onto the central underside portion of thedock platform structure symmetrically in respect to platformlongitudinal centerline Q. The details of connection to the platform andthe means of coupling two or more such ballast tanks together may besimilar in all respects to that described above in respect to pipes 13aand 13b, including the use of reinforcing members 200 and 20d.

The water level normally is at least no higher than the line indicatedat 22 and may, under some circumstances, be even lower. Under suchcondition ballast tanks 19a and 1% are air-filled, and tanks 13a and 13bmay be partially or wholly airor water-filled to achieve desirable trimof the entire dock structure while supporting the vessel indicated at B.The buoyancy imparted to the dock structure by means of air-filled tanks19a and 19b, and sometimes at least portions of 13a and 13b, wouldgenerally be insuflicient to position and maintain the dock in itsoperable state as shown in the drawing. In order to accomplish this,additional positive buoyancy is provided by means of inflated rubberbags 22a and 22b positioned and secured between pipes 13a and 19a, and13b and 1%, respectively. fabricated of a suitable, flexible materialsuch-as rubber, polyethylene, or the like and are of a substantiallywatertight construction. Each of the inflatable bags is secured to theunderside of the platform by means of flexible cables 23 passing throughloops 24 and secured at their ends my means of eyes 26 fastened to theunderside of crossbeams 12 so that the bags themselves are maintained inproper position under the dock when'either in the inflated condition, asshown in the drawing, or

deflated and hence in a relatively flat, flexible and loose condition.When the bags are in their inflated condition, additional buoyancy isprovided to float the entiredry dock facility and vessel thereon. Thedisplacement volume of bags 22a and 22b in their inflated condition, 7

the volume of the air-filled portions of pipes 13a, 13b,

19a and 19b, and that portion of the dock' platform under the surface ofthe water are selected to be at least equal to a volume of water whoseweight is equal .to the weight of the entire floating dock structure,including thepipes, inflatable bags, and necessary supportive andsecuring attachments, and the weight of the vessel and its varioussupportive equipment and personnel positioned on top of the dockplatform.

After a vessel such as that indicated at B on the plat? form of the dockindicated at D in the drawing has been serviced and it is desirable toreturn" the vessel to its ordinary attitude .in the water, the dock maybe submerged as follows:

' Ballast tanks19a and 19b are flooded with water by opening valves 27aand 27b in lines 28a and 28b respectively, fabricated of suitable stockmaterial such as flexible polyethylene, rubber, or other suitabletubing. All valves referred to herein, such as the aforementioned ones,27a and 27b, are accessible to the operator from the pier, dock or otherconvenient place of operation. All air and water lines referred tohereinafter are understood to be fabricated of similar suitable materialand are long enought to service the dock in its submerged and floatingposition. Intake ends, 29a and 29b, of lines 2 8a'and'28b, V

respectively, are positioned under the surface of the water;

The connection of straps 17a and 17b 7 The inflatable bags may be thepurpose and controlled by known means not further described or shown.Upon opening each of valves 27a and 27b water is admitted through lines28a and 28b in the direction of arrows 31a and 31b and hence into eachof the ballast tanks, 19a and 19b. Air is discharged from the ballasttanks by conventional relief means known in the art and not shown nordescribed herein. At the same time, valves 32a and 32b are opened; thelatter valves are connected in lines 33a and 33b, respectively, in fluidcommunication by conventional fittings to inflatable bags 22a and 22b,respectively. Valves 34a and 34b, located in lines 36a and 36b,respectively, which provide fluid communication from tank 19a toinflatable bag 22a, and from tank 1% to 22b, respectively, are turned tothe off position to isolate the inflatable bags pneumatically from theballast tanks. As the ballast tanks take in water, and the buoyancy ofthe floating platform is.reduced so that it sinks, air is forced fromthe inflated bags 22a and 22b to the atmosphere and the entire structureproceeds to submerge.

As mentioned earlier, tanks 13a and 13b may be incorporated as apart ofmy invention either in a sealedoff condition without fluid communicatingmeans of any type, or as trimmer tanks in the manner as exemplified inthe drawing. .In such case, during submergence of the dock, valves 37aand 37b shown in lines 38a and 38b in fluid communication with tanks 13aand 13b, respectively, are also opened with tips 380 and 38d also belowthe surface of the water so that ballast may be taken in the directionof arrows 52a and 52b by these tanks, as necessary, to submerge the dockand to control the rate of descent. In addition, valves 37a and 37b, ofa conventional type suitable for regulating fluid flow in theirrespective lines, may be regulated to control the attitude of the dockas it sinks. When used in this manner, and in any event during allperiods of submergence, valves 39a and 39b, in pneumatic lines 41a and41b, are turned to the otf position to prevent water from going beyondthe point of those valves for reasons that will be apparent hereinafter.Air discharge from tanks 13a and 13b during this period of operation isaccomplished by conventional relief means known in the-art.

After the dock has submerged to a desired depth,

usually the bottom underneath the area where a vessel is to be servicedin dry clock, the hydrostatic pressure imposed on the system normallywill have completely evacuated inflatable bags 22a and 22b to theirflattened, deflated condition. Hence, my invention includes this novelexpediency of using flexible buoyancy assistance bags which provide forreducing the buoyancy of the dock as it is submerged and less buoyancyis desired. By so doing, the entire operation during submergence isgreatly increased in efiiciency. More specifically, the expanded volumeof the inflated bags required to float the dry dock is eliminated duringsubmergence, when such buoyancy is not wanted, and the volume that suchpositive buoyancy tanks might have imposed upon the system is notpresent to require additional ballast during submergence.

Once the dock has submerged free from its supportive position in respectto the vessel indicated at B, the vessel may be moved away and thesystem is ready to accommodate another vessel.

When another vessel is to be serviced by the floating dry dock embodyingmy invention the following procedure is followed:

With the dock submerged in the manner as described above, the vessel tobe serviced is maneuvered into position in the water over the dock.While this maneuvering is occurring, an air compressor such as the oneindicated at 42 powered by motor 43 through appropriate linkageindicated at 44 is turned on to pressurize receiving tank 46. Valves 47aand 47b in pneumatic lines 48a and 48b, respectively, are opened topermit the flow of pressurized air in the direction of arrows 49a and49b. Lines 48a and 48b are in fluid communication with the capped endsof ballast tanks 19a and 19b, respectively, and the air admittedtherethrough under pressure causes expulsion of the ballast waterthrough lines 28a and 28b in the direction of arrows 51a and 51b throughvalves 27a and 27b, already opened during the submergence portion of theworking cycle. Generally, all of the ballast may be expelled from tanks19a and 19b without affecting the overall buoyancy of the system, ornearly so. If under given operating conditions, complete blowing ofballast from tanks 19a and 19b should tend to cause the dock to rise toofar, the compressor action may be halted until the remainder of theascent is desired. In the majority of cases, however, ballast tanks 19aand 19b may be completely evacuated of ballast water while the vesseloverhead is still being maneuvered into position, and additional airpressure may be imparted into the ballast tanks for further ascent aswill be explained.

Assuming that tanks 19a and 19b have been completely evacuated andadditional air may be charged therein by the compressor working at arelatively reduced rate until it reaches its optimum pressure outputlevel. At this point the compressor may be turned off. When the time isat hand to raise the dock further, evacuation valves 32a and 32b inlines 33a and 33b are closed; and valves 34a and 34b in lines 36a and36b between tank 19a and bag 22a and tank 19b and bag 22b, respectively,are opened. The air under pressure in each of the ballast tanks 19a and19b now flows through lines 36a and 36b in the direction of arrows 50aand 50b into bags 22a and 22b until equilibrium pressure is reached inboth the ballast tanks and the inflatable bags which will be a functionof the water depth and the external hydrostatic pressure head imposedthrough the flexible rubber bags. This will normally provide the dockwith positive buoyancy which will cause the entire structure to commenceor continue rising from below. Once positive buoyancy is imparted to thedock by means of the inflatable rubber bag, the dock will continue torise at an increasing rate because of the decrease in hydrostatic forcesurrounding the inflatable bag and its ability to continue expanding dueto its flexibility. In many instances such increased positive buoyancyas the dock continues to rise will be suflicient to support the vesselto be serviced out of the water along with associated equipment andpersonnel. If additional buoyancy is required, however, to raise theplatform to its final operating position, the compressor is permitted tocontinue to charge bags 22a and 22b by imposing additional air underpressure into tanks 19a and 19b with which the bags are in fluidcommunication at this point. The platform then contnues to rise until itemerges under the vessel to be lifted out of the water and supported fordry dock servicing.

When the dock is at or near reflotation, additional trim may .beachieved by either admitting water into tanks'13a and 13b or expellingwater therefrom by opening valves 39a and/ or 39b and charging thosetanks with compressed air thus expelling any water contained there- Ifballast is desired in these tanks, it is merely necessary to take inwater through lines 38a and 38b by opening valves 37a and 37b; in suchinstance, water flows into tanks 13a and 13b in the direction of arrows52a and 52b,

respectively, while air is bled through conventional relief means (notshown) or, alternatively, throughlines 41a and 41b in the direction ofarrows 53a and 53b, respectively. When lines 41a and 41b are used tobleed air after a certain amount of initial evacuation of ballast bycompressor action at a relatively high pressure (which will tend to dropif the dock begins to ascend) but. at a nominal rate of displacement bythe compressor, air may be transferred from the rigid ballast tanks tothe flexible, inflatable bags without further work by the compressoritself. This causes the dock to rise away from the depth at whichmaximum compressor pressure is required, and a compressor with arelatively modest rating at the higher pressure may now continue at ahigher rate of displacement but at a lower output pressure. This is tobe contrasted to the situation where all of the ballast tanks are rigidand a greater amount of ballast water must be expelled at the relativelyhigher pressure existing at the outset of the ascension portion of thecycle. In my,invention the additional Water caused by having all of theballast in rigid tanks is avoided to the degree that I accomplishmaximum buoyancy by the use of the inflatable 'rubber bangs. Moreover, Ihave the added advantage of being able to charge the inflatable rubberbags from the rigid ballast tanks, which are necessary to some degree,while my dry dock structure is rising from the bottom. Thus using mynovel invention a dock may be raised relatively rapidly with a smallercompressor than would normally be required using all rigid ballasttanks, and the dock may be submerged more rapidly by virtue of thedeflatable rubber bags when that portion of the cycle is eflectuated,

As noted briefly above, the structure shown in the.

drawing merely exemplifies one form of my invention and serves toillustrate the modular nature of my novel device. For example, almostany length of dock may be accommodated by merely coupling additionalstructural sections and ballast pipes in the manner described in somedetail at the outset of this specification. In addition it should benoted that the'inflatable rubber bags 22a and 22b are shown as a seriesof individual bags linked together at the connection indicated at 54.Although not shown it is understood that this coupling also providesconventional means for fluid communication between the bags 22b, and,although mostly hidden by the dock platfrom structure, the same appliesto bags 22a shown in the drawing.

To give my dry dock arrangement added stability, a pair of spuds or pipeguides 56a and 56b may be employed, each one slidably secured by meansof guides 57a and 57b to each side of the dock. The bottom of the spuds(-not shown) are suitably secured to the bottom. Toward the top of eachspud a series of holes 58 may be drilled. While the dock is beingraised, the spuds and their sliding guide tend to maintain the dock inproper trim; once the dock is refloated, pin 59 may be placed in thehole nearest the underside of guide 57b (and 57a on the other sidealthough not shown) to hold the dock in the raised position. Othersuitable securing means may b used, and once the dock is thus securedall fluid lines may be closed so that the compressor unit and flexiblelines may be disconnected for use elsewhere.

Although the foregoing specification is in some detail, it is understoodthat this is done for purposes of illustration and is not intended toimpose unnecessary limitations'on my invention which may be practiced innumerous versions within the spirit thereof and scope of the appendedclaims What is claimed is:

1. In a submergible dock to lift and support a vessel out of water, saiddock having a rigid hollow ballast oompartment secured to the undersidethereof, first means to convey water into and out of said compartment,and second means in fluid communication with the atmosphere and saidcompartment to pump air into the compartment and expel water containedtherein through said first means, the improvement comprising, incombination: an inflatable bag collapsible to a deflated condition;fastener means to secure said bag in the inflated and deflated condi- Vfloating; and means in fluid communication with the atmosphe re and saidinflatable bag to pump air into said bag and expand the bag to itsinflated condition, said inflated bag, ballast compartment and waterdisplacing portions of said dock being selected to have a combinedvolume at least' as great as a volume of water having -a weight equal tosaid dock, including said rigid ballast compartment and bag,- and thevessel supported thereon; whereby said dock may be submerged and theinflatable bag deflated when water 7 is conveyed by said first meansinto said ballast compartment, and refloated to lift and support avessel thereon when the water is expelled'from said ballast compartmentby said second means and the inflatable bag is filled with air by saidmeans in fluid communication with the atmosphere and the inflatable bag.

2. A submergible floating dock to lift and support a vessel out ofwater, comprising in combination; a platform; at least two segments ofenclosed hollow pipe in spaced apart relationship to each other andsecured to the underside of said platform; a pneumatically inflatablebag collapsible to a deflated condition when said dock is submergedbelow the surface of the water; means connected in fluid communicationwith said inflat-ablebag to convey air therefrom when said dock is beingsubmerged and block air from being conveyed therefrom when the dock isbeing refloated and floating; means to secure said bag in the inflatedand deflated condition on the underside of said platform; first means influid communication with the water in which said floating dock operatesand said pipe segments to convey water into and out of the pipes, saiddock being imparted with negative buoyancy when water is conveyed intoand fills said pipe segments; a source of compressed air; means in fluidcommunication with said pipe segments and said source of compressed airto pump air into said pipe segments and expel the water containedtherein through said first means; and means in fluid communication withsaid pipe segments into the inflatable 'bag after the pipe segments arefilled with air, thecombined volume of said pneumatically inflatable bagin the inflated condition, the portions of said pipe segments filledwith air and the water" displacing portion of said dock platform whenfloating, being at least 'as great as a volume of water having a weightequil to the entire dock structure and the vessel supported thereon,whereby said dock with a vessel supported thereon is causedto havepositive buoyancyLwhen said pipe segments are filled with air and saidpneumatically inflatable bag is in the inflated condition. a p a 3. Asubmergible floating dock to lift and support a vessel out.of the water,comprising in combination: a platform; a plurality of parallel,enclosed, hollow pipes secured to the underside of said platform, one ofsaid pipes located along a first lower edge of said'platform,

located along the lower edge of the V first lower edge, and at least aone other of said pipes located under the center portion of another ofthe pipes platform opposite to said the platform; first and secondvpneumatically inflatable bags collapsible to a deflated condition; meansto secure said bags in the inflated and deflated condition on oppositesides of saidplatform equidistant from the center of theplatform andimmediately adjacent to the underside when the preselected pipes arefilled with water; a source of compressed air; means in fluidcommunication with said preselected hollow pipes and said source ofcompressed air to convey air under pressure into the preselected hollowpipes and expel water contained therein through said first means; andmeans in fluid communication with said preselected hollow pipes and saidinflatable bags to convey air from the preselected hollow pipes into theinflatable bags after the preselected hollow pipes are filled with air,the combined volume of said pneumatically inflatable bags in theinflated condition, the portions of said preselected pipe segmentsfilled with air, and the water displacing portion of said dock platformwhen floating being at least as great as a volume of water having aweight equalto the entire dock structure and th vessel supportedthereon.

4. The floating dock in accordance with claim 3 and wherein further saidpreselected ones of said hollow pipes also include said pipes locatedalong the first lower edge of said platform and the lower edge of theplatform opposite to said first lower edge.

5. In a submergible dock to lift and support a vessel out of water, saiddock having at least two rigid ballast tanks secured to the undersidethereof, first means to convey water into and out of said tanks, andsecond means in fluid communication with the atmosphere and said tanksto pump air into the tanks and expel water contained therein throughsaid first means, the improvement comprising, in combination: aninflatable bag collapsible to a deflated condition; means to secure saidbag in the inflated and deflated condition to the underside of said dockbetween said ballast tanks; means connected in fluid communication withsaid bag to expel air therefrom when said dock is being submerged andblock air from being expelled when the dock is being refloated andfloating; means in fluid communication with the atmosphere and saidinflatable bag to pump air into said bag and expand the bag to itsinflated condition, said inflated bag, ballast tanks, and waterdisplacing portions of said dock being selected to have a combinedvolume at least as great as a volume of water having a weight equal tosaid dock, including said tanks and bag, and the vessel supportedthereon; whereby said dock may be submerged and the inflatable bagdeflated when water is conveyed by said first means into said ballasttanks, and refloated to lift and support a vessel thereon when the wateris expelled from said ballast tanks by said second means and theinflatable bag is filled with air by said means in fluid communicationwith the atmosphere and the inflatable bag; first and second verticalpipes secured to the ground surface under the water in which said dockoperates, said first pipe aligned in tangential contact with one side ofsaid platform and said second pipe aligned in tangential contact withthe other side of the platform; means secured to each side of said dockand in sliding contact around at least a portion of each of saidvertical pipes to restrain the pipes in tangential and sliding contactwith the sides of the dock; and means to secure said dock to saidvertical pipes and prevent relative motion of the dock in respect to thevertical pipes when the dock is in floating position.

6. A submergible floating dock to lift and support a vessel out ofwater, comprising in combination: a platform; a rigid hollow ballastcompartment secured to the underside of said platform; a pneumaticallyinflatable bag collapsible to a deflated condition when said dock issubmerged below the surface of the water; means connected in fluidcommunication with said inflatable bag to convey air therefrom when saiddock is being submerged and block air from being conveyed therefrom whenthe dock is being refloated and floating; means to secure said bag inthe inflated and deflated condition on the underside of said platform;first means in fluid communication with the water in which said floatingdock operates and said ballast compartment to convey water into and outof the compartment, said dock being imparted with negative buoyancy whenwater is conveyed into and fills said compartment; a source ofcompressed air; means in fluid communication with said compartment andsaid source of compressed air to pump air into the compartment and expelthe water contained therein through said first means; and means in fluidcommunication with said compartment and said inflatable bag to conveyair from the compartment into the inflatable bag after the compartmentis filled with air, the combined volume of said pneumatically inflatablebag in an inflated condition, the portions of said compartment filledwith air and the water displacing portion of said dock platform being atleast as great as a volume of water having a weight equal to at leastthe entire dock structure, whereby said dock is caused to have positivebuoyancy when said compartment is filled with air and said pneumaticallyinflatable bag is in an inflated condition.

7. The submergible dry dock in accordance with claim 6 and whereinfurther the combined volume of said pneumatically inflatable bag in theinflated condition, the portions of said compartment filled with air andthe water displacing portion of said dock platform when floating beingat least as great as a volume of water having a Weight equal to at leastthe entire dock structure and vessel with associated equipment andpersonnel to be supported thereon.

8. The method of submerging and refloating a dry dock operating on andin a body of Water comprising the steps of: pumping water into a firstzone within said dock when floating and simultaneously evacuating theair from and decreasing the water displacing volume of a second zone ofsaid dock, said dock being caused to occupy a volume less than a volumeof water having a weight equal to said entire dock structure, wherebysaid dock submerges in said body of water; and pumping air into saidfirst zone within said dock when submerged until the water is evacuatedtherefrom, and then transferring air from said first zone to said secondzone to increase the water displacing volume of the second zone untilsaid dock is caused to occupy a volume greater than a volume of waterhaving a weight equal to said entire dock structure, whereby said dockbecomes positively buoyant and begins to rise to the surface of saidbody of water, and said second zone continues to increase in waterdisplacing volume and accelerates the rise of said dock to the surfaceof the body of water.

No references cited.

MILTON BUCHLER, Primary Examiner.

A. H. FARRELL, Examiner.

1. IN A SUBMERGIBLE DOCK TO LIFT AND SUPPORT A VESSEL OUT OF WATER, SAIDDOCK HAVING A RIGID HOLLOW BALLAST COMPARTMENT SECURED TO THE UNDERSIDETHEREOF, FIRST MEANS TO CONVEY WATER INTO AND OUT OF SAID COMPARTMENT,AND SECOND MEANS IN FLUID COMMUNICATION WITH THE ATMOSPHERE AND SAIDCOMPARTMENT TO PUMP AIR INTO THE COMPARTMENT AND EXPEL WATER CONTAINEDTHEREIN THROUGH SAID FIRST MEANS, THE IMPROVEMENT COMPRISING, INCOMBINATION: AN INFLATABLE BAG COLLAPSIBLE TO A DEFLATED CONDITION;FASTENER MEANS TO SECURE SAID BAG IN THE INFLATED AND DEFLATED CONDITIONTO THE UNDERSIDE OF SAID DOCK; VALVE MEANS CONNECTED IN FLUIDCOMMUNICATION WITH SAID BAG TO EXPEL AIR THEREFROM WHEN SAID DOCK ISBEING SUBMERGED AND BLOCK AIR FROM BEING EXPELLED WHEN THE DOCK IS BEINGREFLOATED AND FLOATING; AND MEANS IN FLUID COMMUNICATION WITH THEATMOSPHERE AND SAID INFLATABLE BAG TO PUMP AIR INTO SAID BAG AND EXPANDTHE BAG TO ITS INFLATED CONDITION, SAID INFLATED BAG, BALLASTCOMPARTMENT AND WATER DISPLACING PORTIONS OF SAID DOCK BEIGN SELECTED TOHAVE A COMBINED VOLUME AT LEAST AS GREAT AS A VOLUME OF WATER HAVING AWEIGHT EQUAL TO SAID DOCK, INCLUDING SAID RIGID BALLAST COMPARTMENT ANDBAG, AND THE VESSEL SUPPORTED THEREON; WHEREBY SAID DOCK MAY BESUBMERGED AND THE INFLATABLE BAG DEFLATED WHEN WATER IS CONVEYED BY SAIDFIRST MEANS INTO SAID BALLAST COMPARTMENT, AND REFLOATED TO LIFET ANDSUPPORT A VESSEL THEREON WHEN THE WATER IS EXPELLED FROM SAID BALLASTCOMPARTMENT BY SAID SECOND MEANS AND THE INFLATABLE BAG IS FILLED WITHAIR BY SAID MEANS IN FLUID COMMUNICATION WITH THE ATMOSPHERE AND THEINFLATABLE BAG.